Metal Organic Framework Cu3 Research Articles

Propargylamine synthesis via sequential methylation and C–H functionalization of N-methylanilines and terminal alkynes under metal–organic framework Cu2(BDC)2(DABCO) catalysis

A crystalline porous metal–organic framework Cu2(BDC)2(DABCO) was synthesized and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), hydrogen temperature-programmed reduction (H2-TPR), and nitrogen physisorption measurements. The Cu2(BDC)2(DABCO) was used as a heterogeneous catalyst for the direct C–C coupling reaction via cascade methylation and C–H functionalization of N-methylaniline and terminal alkynes. tert-Butyl hydroperoxide also served as the methylating reagent in the transformation, and N-methyl-N-(3-phenylprop-2-ynyl)benzenamine but not N-(3-phenylprop-2-ynyl)benzenamine was produced as the principal product. The Cu-MOF could be recovered and reused several times without a significant degradation in catalytic activity. To the best of our knowledge, the direct oxidative C–C coupling between N-methylaniline and alkynes with methylation transformation was not previously mentioned in the literature.

A Metal–Organic Framework Cu2(BDC)2(DABCO) as an Efficient and Reusable Catalyst for Ullmann-Type N-Arylation of Imidazoles

A highly porous metal–organic framework (Cu2(BDC)2(DABCO)) was synthesized and used as an efficient and recyclable heterogeneous catalyst for the Ullmann-type N-arylation of aryl halides with imidazoles. The Cu2(BDC)2(DABCO) was characterized by several techniques, including X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared, atomic absorption spectrophotometry, and nitrogen physisorption measurements. The catalyst offered high activity under mild conditions, confirming outstanding advantages when employing the Cu2(BDC)2(DABCO) as catalyst for Ullmann-type N-arylation reaction. The catalyst could be separated from the reaction mixture by simple filtration, and could be reused without a significant degradation in catalytic activity.

Guest Adsorption in the Nanoporous Metal–Organic Framework Cu3(1,3,5-Benzenetricarboxylate)2: Combined In Situ X-ray Diffraction and Vapor Sorption

The structure of the nanoporous metal–organic framework Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) with a variety of molecular guests was studied in situ using single crystal X-ray diffraction. By collecting crystal structure data for a series of guests within the same host crystal, insights into the molecular interactions underpinning guest adsorption processes have been gained. Adsorption behaviors are influenced strongly by both enthalpic and entropic thermodynamic, as well as interpore steric (size-exclusion) effects, and we note correlations between guest attributes and these effects. Vapor adsorption measurements revealed a guest uptake capacity inversely proportional to guest size. Correspondingly, structural results show that guests reside in the smallest pores accessible to them. Interpore steric effects for larger guests cause these to be excluded from the smallest pores, and this corresponds to lower total uptake. Both hydrophilic and lipophilic small guests adsorb favorably into the 5 A dia...

New CO2 separation membranes containing gas-selective Cu-MOFs

We examined the challenge of preparing CO2-selective bifunctional three-dimensional Cu-metal–organic frameworks (Cu-MOFs) for use in mixed-matrix membranes (MMMs) fabricated on an asymmetric polymer support. Two different gas-selective micro-sized frameworks, [{Cu2(Glu)2(µ-bpa)}·(CH3CN)]n (Cu-MOF1) and [{Cu2(Glu)2(µ-bpp)}·(C3H6O)]n (Cu-MOF2) (Glu=glutarate, bpa=1,2-bis(4-pyridyl)ethane, bpp=1,3-bis(4-pyridyl)propane), were synthesised and dispersed in polyoxazoline (POZ), as a matrix for the fabrication of the MMMs. SEM imaging indicated relatively good adhesion between the Cu-MOFs and POZ, without any surface treatment. The ideal selectivity of CO2/N2 was enhanced significantly in the Cu-MOF/POZ MMM, compared to that in a pristine POZ asymmetric membrane. Improvement in the CO2/N2 selectivity of the membranes was achieved via both high adsorption selectivity of CO2 over N2 by the Cu-MOFs, and the difference in pore sizes. The fabrication methods that use gas-selective MOFs may create new opportunities for gas-selective MOF/polymer combinations for MMMs with useful properties for large volume separations.

Ligand-free direct C-arylation of heterocycles with aryl halides over a metal-organic framework Cu2(BPDC)2(BPY) as an efficient and robust heterogeneous catalyst

A crystalline porous metal-organic framework Cu2(BPDC)2(BPY) was synthesized and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), hydrogen temperature-programmed reduction (H2-TPR), and nitrogen physisorption measurements. The Cu2(BPDC)2(BPY) exhibited high catalytic activity in direct CH arylation reactions between heterocyles and aryl halides. The Cu2(BPDC)2(BPY)-catalyzed CH arylation reaction could proceed to higher conversion than that of the reaction using Cu3(BTC)2, Cu(BDC), Cu(BPDC), and Cu2(BDC)2(BPY) as catalyst. Furthermore, under our conditions, the Cu2(BPDC)2(BPY) also exhibited significantly higher activity than that of common copper salts, including Cu(NO3)2, CuCl, CuCl2, and CuI. Excellent reusability of the Cu-MOF in the direct heterocycle CH arylation reaction was achieved.

Selective Catalytic Oxidation of Diphenol by Metal-Organic Frameworks Cu3(BTC)2 Using Hydrogen Peroxide

Selective Catalytic Oxidation of Diphenol by Metal-Organic Frameworks Cu3(BTC)2 Using Hydrogen Peroxide

Three-dimensional copper (II) metal–organic framework with open metal sites and anthracene nucleus for highly selective C2H2/CH4 and C2H2/CO2 gas separation at room temperature

A new three-dimensional micro-porous metal–organic framework Cu2(ADDI) (ZJU-26; H4ADDI=5,5′-(anthracene-2,6-diyl) diisophthalic acid) with open metal sites and suitable pore space for their interactions with acetylene molecules was solvothermally synthesized and structurally characterized. ZJU-26 reveals a three-dimensional structure having hexagonal pores of about 5.0Å along the c axis and irregular pores of about 3.4×8.5Å2 along the a or b axis. Due to the introduction of anthracene ring do significantly enlarge pore size along a/b axis and enhance the interaction between MOF and acetylene, ZJU-26 indicates large adsorption enthalpies of 32.7kJ/mol for C2H2 and moderately high acetylene uptake of 84cm−1/g, highlighting ZJU-26 as the highly selective microporous metal organic framework for the C2H2/CH4 and C2H2/CO2 gas separation with separation selectivity of 45.9 and 12.5 at room temperature.

Investigation of the spin-lattice relaxation of 13CO and 13CO2 adsorbed in the metal-organic frameworks Cu3(btc)2 and Cu3−xZnx(btc)2

The (13)C nuclear spin-lattice relaxation time of (13)CO and (13)CO2 molecules adsorbed in the metal-organic frameworks (MOFs) Cu2.97Zn0.03(btc)2 and Cu3(btc)2 is investigated over a wide range of temperatures at resonance frequencies of 75.468 and 188.62 MHz. In all cases a mono-exponential relaxation is observed, and the (13)C spin-lattice relaxation times (T1) reveal minima within the temperature range of the measurements and both frequencies. This allows us to carry out a more detailed analysis of the (13)C spin relaxation data and to consider the influence due to the spectral functions of the thermal motion. In a model-free discussion of the temperature dependence of the ratios T1 (T)∕T1,min we observe a motional mechanism that can be described by a single correlation time. In relation to the discussion of the relaxation mechanisms this can be understood in terms of dominating translational motion with mean jump distance being larger than the minimum distances between neighboring adsorption sites in the MOFs. A more detailed discussion of the jump-like motion observed here might be carried out on the basis of self-diffusion coefficients. From the present spin relaxation measurements activation energies for the local motion of the adsorbed molecules in the MOFs can be estimated to be 3.3 kJ∕mol and 2.2 kJ∕mol, for CO and CO2 molecules, respectively. Finally, our findings are compared with our recent results derived from the (13)C line shape analysis.

Ligand‐Free Copper‐Catalyzed Coupling of Phenols with Nitroarenes by using a Metal–Organic Framework as a Robust and Recoverable Catalyst

AbstractA highly porous metal–organic framework Cu2(BDC)2(DABCO) (H2BDC=1,4‐benzenedicarboxylic acid, DABCO=1,4‐diazabicyclo[2.2.2]octane) was synthesized and used as an efficient recyclable heterogeneous catalyst for the coupling reaction of phenols with nitroarenes to form diaryl ethers without using a ligand. Physical characterization of the MOF was obtained by using XRD, SEM, TEM, thermogravimetric analysis (TGA), FTIR spectroscopy, atomic absorption spectrophotometry (AAS), H2 temperature‐programmed reduction (H2‐TPR), and N2 physisorption measurements. The Cu2(BDC)2(DABCO)‐catalyzed coupling reaction offers several advantages compared to the conventional Ullmann reaction for the synthesis of unsymmetrical diaryl ethers. To the best of our knowledge, the ligand‐free Cu‐catalyzed O‐arylation reaction of phenols with nitroarenes that uses a heterogeneous catalyst has not been mentioned previously in the literature.

Adsorption of Small Molecules on Cu3(btc)2 and Cu3–xZnx(btc)2 Metal–Organic Frameworks (MOF) As Studied by Solid-State NMR

Static and MAS 13C NMR techniques are used to investigate the interaction of CO and CO2 molecules with the host structure of the MOFs Cu3(btc)2 and Cu2.97Zn0.03(btc)2. A defined amount of 13C-enriched molecules per copper atom was adsorbed. The 13C chemical shift anisotropy and isotropic chemical shift were studied over a temperature range from 10 to 353 K. Already above 30 K an isotropic line for CO is found superimposed to the solidlike spectra belonging to the majority of adsorbed CO molecules. For adsorbed CO2 an isotropic line can be detected above 70 K. This observation reflects differences in the local motion of both molecules. At high temperatures it is found that CO is desorbed more easily from the MOF framework in comparison to CO2. This is in agreement with conclusions derived from desorption measurements on Cu3(btc)2. From the temperature dependence of the chemical shift for adsorbed CO2 molecules (measured by means of 13C MAS NMR between 213 and 353 K) and from the deconvolution of the overla...

Effects of pelletization pressure on the physical and chemical properties of the metal–organic frameworks Cu3(BTC)2 and UiO-66

The metal–organic frameworks CuBTC and UiO-66 were pressed at 1000 and 10,000psi as a first step to engineering particles for use in toxic chemical removal applications. Materials characterization was conducted on each material using powder X-ray diffraction, attenuated total reflectance – Fourier transform infrared spectroscopy, and nitrogen porosimetry. Neither material showed signs of structural degradation during pressing. The CuBTC pressed materials show reduced porosity after pressing, while the UiO-66 surface area remained consistent for all pressed samples. Small-scale breakthrough testing was conducted with CuBTC against ammonia, which probes the reactive sites, and UiO-66 against octane, which probes physical adsorption capacity. Even with the decrease in surface area, the CuBTC materials had consistent ammonia removal capacities, while the UiO-66 pressed materials showed a slight decrease in octane loadings. Data indicate that pressing these MOFs into pellets without a binder is a viable approach to engineering particles in support of filtration and other applications.

Hydrogen adsorption on microporous materials at ambient temperatures and pressures up to 50 MPa

High surface area microporous adsorbents are often proposed as potential hydrogen storage materials, although typically at 77 K and less than 5 MPa. In this study, we focus on conditions more suitable for automotive applications by investigating the storage capacities of microporous materials at 298 K and at pressures up to 50 MPa. In an effort to derive trends within and across material classes, we examined a wide range of materials with varying microstructures including the activated carbons AX-21, KUA-5, and MSC-30; a zeolite templated carbon; a hypercrosslinked polymer; and the Metal Organic Frameworks MOF-177, IRMOF-20, MIL-53, ZIF-8, and Cu3(btc)2. The peak excess adsorption of these materials ranged from 0.8–1.8 wt.%, although many did not reach their maximum capacity even at high pressures. However, the total volumetric storage gains over compressed hydrogen gas were quite low and, in many cases, negative. In addressing ambient temperature adsorption at significantly higher pressures than previously reported, our data confirms and extends the range of validity of several existing DFT calculations. Furthermore, our data suggest that, for both activated carbons and MOFs, factors other than specific surface area govern ambient temperature adsorption capacity. Contrary to some reports, the high fractions of sub-nanometer pores in some of the investigated MOFs did not appear to enhance the excess adsorption even at high pressures. For on-board applications with ambient temperature storage, significant enhancements to the attractive force at the materials’ surface are required, beyond merely increasing specific surface area, or for MOFs, tuning of pore sizes.

Ultrasensitive Humidity Detection Using Metal–Organic Framework-Coated Microsensors

The use of metal-organic framework (MOF) thin films to detect water vapor across a wide concentration range is demonstrated using MOF-functionalized quartz surface acoustic wave (SAW) sensors. A range of 3-14,800 ppmv was obtained with thin films of the MOF Cu(3)(benzenetricarboxylate)(2) (Cu-BTC) deposited by an automated layer-by-layer method. Devices coated by a manual technique demonstrated sensitivity from 0.28 to 14,800 ppmv, the limit of our test system. This exceeds the sensitivity of many commercially available sensors. Cu-BTC layers were covalently bonded directly to the silicon oxide surface, allowing devices to be heated beyond 100 °C to desorb water adsorbed in the pores without decomposition, thereby regenerating the sensors. Sensor response as a function of coating thickness was evaluated, showing that the SAW sensor response is bounded by maximum and minimum layer thicknesses. Computer simulation of H(2)O uptake shows a multistep adsorption isotherm defined by initial adsorption at open Cu-sites, followed by pore-filling and finally full saturation. Modeling and experimental results are consistent. Calculated uptake values suggest an efficient adsorption of H(2)O by Cu-BTC. These results provide the first convincing evidence that MOF functionalization of compact sensing technologies such as SAW devices and microcantilevers can compete with state-of-the art devices.

Catalytic activity of metal organic framework Cu3(BTC)2 in the cycloaddition of CO2 to epichlorohydrin reaction

We demonstrate the novel, catalytic activity of metal organic framework of Cu3(BTC)2 catalysts in the synthesis of chloropropene carbonate from CO2 and epichlorohydrin. The catalysts display moderate epoxide conversions, and moderate selectivities to chloropropene carbonate at 100°C. No solvents or co-catalysts were required. It is suggested that Lewis acid copper (II) sites in the Cu3(BTC)2 framework promoted the adsorption of carbon dioxide on the solid surface and its further conversion to the carbonate.

Formation of a nanohybrid composite between mesostructured cellular silica foam and microporous copper trimesate

A metal-organic framework HKUST-1 or Cu3(BTC)2 was synthesized in mesopores of a COOH functionalized mesostructured cellular silica foam (MCF(M)-COOH), resulting in a hydrophobic nanocomposite. The Cu3(BTC)2 formed in the MCF(M)-COOH has been prepared by a microwave method with sequential incorporation of copper nitrate and 1,3,5-benzenetricarboxylic acid in a water/ethanol mixture containing the MCF(M)-COOH. The nanocomposite was characterized by XRD, BET, FT-IR, TEM and solid state 13C NMR. The nanocomposite had a higher hydrophobic property than pure Cu3(BTC)2 and MCF(M)-COOH as a result of their hybridization. Moreover, the formation of the nanocomposite increased the sorption rate of cyclohexane vapor as compared with those of pure Cu3(BTC)2 and MCF(M)-COOH due to the increased hydrophobicity.

Methods for Computing Accurate Atomic Spin Moments for Collinear and Noncollinear Magnetism in Periodic and Nonperiodic Materials.

The partitioning of electron spin density among atoms in a material gives atomic spin moments (ASMs), which are important for understanding magnetic properties. We compare ASMs computed using different population analysis methods and introduce a method for computing density derived electrostatic and chemical (DDEC) ASMs. Bader and DDEC ASMs can be computed for periodic and nonperiodic materials with either collinear or noncollinear magnetism, while natural population analysis (NPA) ASMs can be computed for nonperiodic materials with collinear magnetism. Our results show Bader, DDEC, and (where applicable) NPA methods give similar ASMs, but different net atomic charges. Because they are optimized to reproduce both the magnetic field and the chemical states of atoms in a material, DDEC ASMs are especially suitable for constructing interaction potentials for atomistic simulations. We describe the computation of accurate ASMs for (a) a variety of systems using collinear and noncollinear spin DFT, (b) highly correlated materials (e.g., magnetite) using DFT+U, and (c) various spin states of ozone using coupled cluster expansions. The computed ASMs are in good agreement with available experimental results for a variety of periodic and nonperiodic materials. Examples considered include the antiferromagnetic metal organic framework Cu3(BTC)2, several ozone spin states, mono- and binuclear transition metal complexes, ferri- and ferro-magnetic solids (e.g., Fe3O4, Fe3Si), and simple molecular systems. We briefly discuss the theory of exchange-correlation functionals for studying noncollinear magnetism. A method for finding the ground state of systems with highly noncollinear magnetism is introduced. We use these methods to study the spin-orbit coupling potential energy surface of the single molecule magnet Fe4C40H52N4O12, which has highly noncollinear magnetism, and find that it contains unusual features that give a new interpretation to experimental data.

Molecular chemisorption on open metal sites in Cu3(benzenetricarboxylate)2: A spatially periodic density functional theory study

Chemical interactions of H(2)O, CO, NO, pyridine, C(2)H(2), H(2)S, and NH(3) with open metal sites in the metal-organic framework (MOF) Cu(3)(benzenetricarboxylate)(2) are examined using plane wave periodic density functional theory (DFT). In the case of single molecule adsorption on a Cu dimer, NH(3) and pyridine have the strongest binding, while NO binds weakly. Binding of pairs of molecules on a Cu dimer shows significant interaction energies, that is, the binding energy of the pair of molecules is not a simple summation of the binding energies of each molecule. The effect of molecular adsorption on the magnetic moments of Cu atoms in the MOF is also examined. Using the binding energies from DFT calculations, the effects of the pressure and temperature on the chemisorbed species are investigated. Finally the effect of water adsorption on the elastic behavior of Cu(3)(BTC)(2) is described.

A peanut-like Keggin-type POM-incorporated metal-organic framework

Abstract A novel peanut-like POM-based metal-organic framework Cu3(BIMB)5(BIM)2(PMo12O40)2 has been successfully constructed. The metal-organic framework forms a peanut-like shell and {PMo12} anions embed in the voids to act as cores. The whole framework can be simplified as a (4,5)-connected 3D topology. In addition, we investigated the optical band gap of the title compound 2.84 eV.

Temperature swing adsorption of NOx over Keggin type heteropolyacids

Temperature swing NOx adsorption–desorption cycles with gas mixtures consisting of 1000 ppm NOx, 5% O2, 3% H2O and N2 were carried out on heteropolyacid adsorbents in the temperature range 80–170 °C. Keggin type heteropolyacids having tungsten, molybdenum or their combination in octahedral coordination in combination with P, Si, Ge or B atoms in tetrahedral coordination were investigated. The heteropolyacids were used as pure compounds or supported on zeolite Y or the metal–organic framework Cu3(BTC)2 (BTC represents 1,3,5-benzenetricarboxylic acid). The property of reversible adsorption of equimolar mixtures of NO and NO2 was observed with Keggin type heteropolyacids based on W and combinations of W and Mo. Regeneration of the saturated adsorbent was achieved by cooling in a water vapor containing gas stream. The investigated heteropolyacids showed different water adsorption behavior. The capability of NOx adsorption was found to be related with crystal hydrate formation. Crystal water was much stronger retained in W-based compared to Mo-based Keggin compounds. Co-adsorption of NO and NO2 molecules occurred only on Keggin compounds containing crystal water. The formation of H2NO2+ compound out of NO, NO2 and H2O in the interstitial spaces between Keggin units is proposed. The H-form and Co, Cu, Fe, Ni and Mn salts of Wells–Dawson type heteropolyacids were found to be readily dehydrated upon heating and did not show reversible NOx adsorption. Supported W-based Keggin heteropolyacid showed lower NOx adsorption capacity compared to the unsupported heteropolyacid.

MOF@PolyHIPEs

A macroporous polyHIPE was used as a monolithic support to grow crystals of the metal-organic framework Cu3(btc)2 (btc = benzene-1,3,5-tricarboxylate) directly within the open-cell structure. Due to the creation of a microporous structure within a macroporous substrate, a material with a lung-like porous structure is obtained (see picture: SEM micrograph of Cu3(btc)2 crystals in polyHIPE).